Used In Real-time Three-dimensional Echocardiography Time Gain Op Amp

The transesophageal echocardiogram is used in the diagnosis of heart disease. It could provide high quality image for the heart of human being. It makes use of ultrasonic imaging, a popular and safe technique in medical diagnostics. Ultrasonic imaging is based on the pulsed-echo principle. Ultrasound waves generated by ultrasonic transducers with frequencies in the order of several MHz are transmitted into the tissue under examination. Next, the transducers are working as receivers to receive the echo signals and convert them into the electrical domain. The echo signals in the electrical domain are further processed to construct images.Our research project is to design a transesophageal probe using a matrix ultrasonic transducer for 3D echocardiography. Due to the large element count (2000) of this transducer, it is necessary to locally combine the signals of several elements and thus reduce the number of cables through the gastroscopic tube. This requires simple and low-power electronics close to the transducer. An important function of these electronics is to compensate for the time-dependent attenuation of the ultrasound wave due to scattering, absorption and other propagation effects. This so-called time-gain-compensation (TGC) is required to maintain image uniformity and relaxes the dynamic-range requirements in the remainder of the readout chain. This thesis presents a low-power amplifier that provides the programmable gain required for TGCThe TGC amplifier has been designed in a standard 0.35μm CMOS technology. Simulation results show that it provides a bandwidth of 15MHz when driving 250fF load. With an input referred noise of 45μVrms, the amplifier can handle input echo signals centered at 6MHz with 80dB dynamic range (100μV to 1V). Monte-Carlo simulation shows that the gain error at 6MHz is below 1dB for all gain settings. The TGC amplifier consumes only 130μW from a power supply of 3.3V.The TGC demonstrates a good overall performance in terms of noise, gain accuracy and circuit complexity. Compared with the prior art, this design reduces the power consumption by a factor of 15, thus enabling the integration of 1000's of readout channels on a single matrix-transducer readout chip.